Combustion chamber of a gas turbine

ABSTRACT

A combustion chamber of a gas turbine, with at least one shingle that including a plate-shaped shingle body that has a circumferential shingle edge which is raised from the side that is facing away from the combustion chamber interior space, and which abuts against a combustion chamber wall in the mounted state of the shingle, wherein the shingle body is provided with an arrangement of effusion cooling holes, and the combustion chamber wall is provided with an arrangement of impingement cooling holes in the area of the shingle, wherein the arrangement of impingement cooling holes has a lateral distance to the shingle edge that is between 1.5 and 2 times the distance of the surface of the combustion chamber wall to the surface of the shingle body, and that the distance of the arrangement of impingement cooling holes is between 1.1 and 3 times the lateral distance in the corner areas of the shingle.

The invention relates to a combustion chamber of a gas turbine according to the features of the generic term of claim 1.

Specifically, the invention relates to a combustion chamber of a gas turbine which is covered with shingles. At least one shingle comprises a plate-shaped shingle body which has a circumferential shingle edge. It extends from the cold side of the shingle body that is facing away from the combustion chamber's interior space to the combustion chamber wall and thus forms an intermediate space between the shingle body and the combustion chamber wall. Cooling air is introduced into this intermediate space through impingement cooling holes, and is subsequently discharged through effusion cooling holes of the shingle body located at its surface. For this purpose, the shingle body is provided with an arrangement of effusion cooling holes, which may for example be embodied in a row-shaped manner or with another arrangement with respect to each other. The impingement cooling holes of the shingle wall are also embodied in a suitable arrangement.

As for the state of the art, at first EP 0 576 435 B1 is referred to. It shows a structure that is illustrated in FIG. 2. Here, it is shown that a shingle 25 has a substantially plate-shaped shingle body 29 that is delimited by a shingle edge 31. The shingle edge 31 extends from the shingle body 29 in the direction towards the combustion chamber wall 32 to form an intermediate space 35. The combustion chamber wall 32 is provided with impingement cooling holes 34 to introduce cooling air into the intermediate space 35. This cooling air flows out of the intermediate space 35 through the effusion cooling holes 33 that are formed in the shingle body 29. Due to the fact that the shingle edge 31 cannot be arranged in a sealing manner at the combustion chamber wall 32, there is always a leakage, which is illustrated as leakage air 36. Thus, a part of the air volume that is supplied through the impingement cooling holes 34 flows from the intermediate space 35 unused as leakage air 36, and cannot be used to flow through the effusion cooling holes 33.

FIG. 3 shows a similar structure, wherein the same parts are indicated by the same reference signs. With regard to this, reference is made to U.S. Pat. No. 5,598,697 A. Although this construction differs from the constructional principles according to the invention, it shows that either leakage air 36 flows out of the intermediate space 35 and cannot be used for effusion cooling holes 33, or a seal 38 has to be used.

The sealing of the impingement cooling cavity by means of an additional seal is also known from EP2354660 (rigid seal), EP1310735 (elastic seal), U.S. Pat. No. 7,140,185 (coating). Common to all seal-based solutions are the higher costs resulting from the manufacture of the seal, the greater mounting effort due to the mounting of the seal, and the risk of the seal failing.

Thus, in the state of the art there is the problem that a sealing of the intermediate space between the shingle and the combustion chamber wall is not possible without additional effort, or is only possible to a limited extent. This results in a leakage air or leakage flow, as a result of which cooling air flows unused from the intermediate space between the combustion chamber wall and the shingle body, and is not available for cooling through the effusion cooling holes.

Further, EP 1 351 022 B1 is quoted as the state of the art.

The invention is based on the objective of creating a combustion chamber of a gas turbine which ensures an effective use of the cooling air in the area of the shingle, while at the same time having a simple structure and a single, cost-effective manufacturability.

According to the invention, the objective is achieved by a combination of features of claim 1, with the subclaims showing further advantageous embodiments of the invention.

Thus, it is provided according to the invention that the arrangement of impingement cooling holes has a distance to the shingle edge which lies between 1.5 to 2 times the distance of the surface of the combustion chamber wall to the surface of the shingle body, and that in the corner areas of the shingle the distance of the arrangement of impingement cooling holes is between 1.1 and 3 times the above-mentioned distance.

The invention is based on the basic principle of designing the inflow of cooling air into the intermediate space formed by the shingle in such a manner that the supply of cooling air through the impingement cooling holes occurs in the middle area of the shingle body, i.e. up to a distance from the shingle edge. As the effusion cooling holes extend across the entire surface of the shingle body, the cooling air can be discharged through the sufficiently dimensioned effusion cooling holes. This flow of air is caused by the resulting pressure difference across the shingle. In a completely sealed shingle edge, the air flows though all of the effusion bore holes, without any dead bands of the flow being formed. In a complete sealing, the pressure gradient in the intermediate space causes only very small amounts of air to flow as leakage air via the shingle edge. In total, there is thus little reason why the cooling air flowing in through the impingement cooling holes should enter as leakage air via the shingle edge.

In the constructions of double-wall combustion chambers as they are already known from the state of the art, the shingle is usually bolted onto the combustion chamber wall without any seals. Such seals would be elaborate and cost-intensive. In addition, thermal expansions and contractions always lead to minor gap formation. In addition, manufacturing tolerances also exclude a completely sealed abutment of the shingle edge at the combustion chamber wall. Further, it should be noted that the geometry of combustion chambers of gas turbines is very complex and does not always allow for a complete sealing of the shingle edge. In this context, it is to be understood that the person skilled in the art knows what is to be understood by the term “gas turbine”, namely an aircraft gas turbine or a stationary gas turbine. The invention can be used with both. Thus, the solution according to the invention makes it possible to use substantially the entire volume of cooling air for the purpose of cooling the shingles, namely, on the one hand, for cooling the cold surface of the shingle that is facing away from the combustion chamber interior space by means of impingement cooling and, on the other hand, for film cooling by means of the air that is discharged through the effusion cooling holes. Since what results according to the invention is a considerable or complete reduction of the leakage flow, the present invention results in a considerable increase of the efficiency of the shingle cooling.

Thus, it is provided according to the invention that the impingement cooling holes are not formed up to the shingle edge, but that the arrangement of impingement cooling holes is chosen in such a manner that each impingement cooling hole has a distance from each shingle edge through which a leakage may occur. This distance is chosen in such a manner that it is defined based on the free jet length of the impingement cooling jet. The free jet length is the path length between the exit site of the cooling air from the impingement cooling hole and impingement site on the cold surface of the shingle body that is facing away from the combustion chamber's interior space. The volume of the intermediate space between the combustion chamber wall and the shingle body is also defined based on this free jet length. According to the invention, the distance of the impingement cooling holes from the shingle edge is dimensioned in such a manner that it corresponds to at least 1.5 times the free jet length of the impingement cooling jet. The distance can be up to 2 times the free jet length, with this value being a preferred value. Thus, by defining the distance it is thus ensured that a sufficient number an effusion holes is present between the edge area of the arrangement with impingement cooling holes or of the field which is formed by the impingement cooling holes and the shingle edge. The cooling air which is discharged through the edge-side impingement cooling holes and wants to move in the direction towards the shingle edge thus impinges on a sufficient number of effusion holes and can be discharged through them. Thus, any discharge of this air flow in the form of leakage air is avoided.

Combustion chamber shingles are usually formed in a rectangular, more seldom in an triangular or diamond-shaped, manner. The result is a corner area of the shingle edges in the two neighboring edge areas, which meet in the corner area and in which no impingement cooling holes are present, meet. To ensure that a sufficient outflow of the impingement cooling air through the effusion cooling holes is ensured also in the corner areas, it must be considered that, according to the invention, the edge distances between the shingle edge and the arrangement of impingement cooling holes are linearly added. According to the invention, a bevel or rounding is formed here in the arrangement of the impingement cooling holes. According to the invention, in an advantageous embodiment this beveled or rounded area is defined by a factor that can be referred to as the overlay constant. This overlay constant has a value of 1.1 to 3, preferably of 1.5 to 2.5, ideally of 2. The distance in the corner area is enlarged by the factor of the overlay constant to ensure that the intermediate space between the shingle body and the combustion chamber wall is passed by the flow to the desired extent.

Thus, according to the invention a smaller projected surface results for the arrangement of impingement cooling holes than for the arrangement of effusion cooling holes. The arrangement of impingement cooling holes is thus shifted away from the shingle edge, and is set at a distance to the same. To ensure a reliable through-flow of cooling air as well as the generation of a suitable pressure gradient in this embodiment, it is possible according to the invention to respectively form the impingement cooling holes with an enlarged diameter as compared to the embodiment according to the state of the art, in which the arrangement of impingement cooling holes extends across the entire surface of the shingle. As an alternative, it is also possible to provide a larger number of impingement cooling holes as compared to the state of the art in order to supply the cooling air volume. Here, the impingement cooling holes can be set closer to each other in the area of the arrangement of impingement cooling holes to avoid any impingement cooling holes located close to the edge within the distance to the shingle edge.

In the following, the invention is explained based on the exemplary embodiments in connection with the drawing. Herein:

FIG. 1 shows a schematic rendering of a gas turbine engine according to the present invention,

FIG. 2 shows a rendering of the state of the art,

FIG. 3 shows a rendering of the state of the art,

FIG. 4 shows a schematic side view of a first exemplary embodiment of the invention,

FIG. 5 shows a rendering of a further exemplary embodiment of the invention, which is analogous to FIG. 4,

FIG. 6 shows a simplified rendering, which is analogous to FIG. 5, including a rendering of possible leakage flows,

FIG. 7 shows a top view of a first exemplary embodiment of the corner design, and

FIG. 8 shows a view of a further exemplary embodiment, which is analogous to FIG. 7.

The gas turbine engine 10 according to FIG. 1 represents a general example of a turbomachine in which the invention may be used. The engine 10 is configured in a conventional manner and comprises, arranged successively in flow direction, an air intake 11, a fan 12 that rotates inside a housing, a medium-pressure compressor 13, a high-pressure compressor 14, a combustion chamber 15, a high-pressure turbine 16, a medium-pressure turbine 17, and a low-pressure turbine 18 as well as an exhaust nozzle 19, which are all arranged around a central engine axis 1.

The medium-pressure compressor 13 and the high-pressure compressor 114 respectively comprise multiple stages, of which each has an arrangement of fixedly arranged stationary guide vanes 20 that extends in the circumferential direction, with the stationary guide vanes 20 being generally referred to as stator vanes and projecting radially inward from the core engine shroud 21 through the compressors 13, 14 into a ring-shaped flow channel. Further, the compressors have an arrangement of compressor rotor blades 22 that project radially outward from a rotatable drum or disc 26, and are coupled to hubs 27 of the high-pressure turbine 16 or the medium-pressure turbine 17.

The turbine sections 16, 17, 18 have similar stages, comprising an arrangement of stationary guide vanes 23 projecting radially inward from the housing 21 through the turbines 16, 17, 18 into the ring-shaped flow channel, and a subsequent arrangement of turbine blades/vanes 24 projecting outwards from the rotatable hub 27. During operation, the compressor drum or compressor disc 26 and the blades 22 arranged thereon as well as the turbine rotor hub 27 and the turbine rotor blades/vanes 24 arranged thereon rotate around the engine central axis 1.

FIGS. 4 to 6 respectively show simplified sectional views in a sectional plane that comprises the central axis of a combustion chamber 15, which is not shown. Here, a combustion chamber wall 32 provided with an arrangement of impingement cooling holes 34 is shown in a schematic manner. With a view to simplifying the rendering, the impingement cooling holes 34 as well as the effusion cooling holes 33, which will be described in the following, are shown only by the flow direction in the form of a flow arrow.

Shingles 25 are arranged at a side of the combustion chamber wall 32 that is facing towards the combustion chamber interior space 30, being for example screwed on, as it is shown in FIG. 2. The shingles have a plate-shaped, substantially flat shingle body 29 that is provided with effusion cooling holes 33. At the edge area of the shingle body 29, a circumferential shingle edge 31 is formed, abutting the combustion chamber wall 32. The height of the shingle edge 31 defines the volume of an intermediate space 35 into which the impingement cooling air flows and is subsequently discharged through the effusion cooling holes 33. The height of the intermediate spaces 35, and thus the volume of the intermediate space 35, is defined by the free jet length L of the impingement cooling air or of the impingement cooling jet that is shown in FIGS. 4 and 5.

As shown in FIGS. 4 to 6, the arrangement of impingement cooling holes 34 is arranged at a distance A from the shingle edge 31. The effusion cooling holes 33 are distributed about the entire surface of the shingle body 29.

FIG. 4 shows an exemplary embodiment in which the ratio of the number of impingement cooling holes to the effusion cooling holes is 1:1. According to the invention, the distance A is chosen in such a manner in this exemplary embodiment that a row of effusion cooling holes is located between the edge of the next impingement cooling hole 34 and the shingle edge 31, as shown in the right-hand half of FIG. 4.

In the exemplary embodiment shown in FIG. 5, the ratio of impingement cooling holes to the effusion cooling holes is 1:2. Consequently, two rows of effusion cooling holes 33 are provided in the distance area A between the shingle edge 31 and the arrangement of impingement cooling holes 34.

If a ratio of impingement cooling holes to effusion cooling holes is 1:3, three rows of effusion holes would be present in the distance area A. This embodiment is not shown.

FIG. 6 shows a rendering that is analogous to FIG. 5 and from which it can be seen that, in the most unfavorable case, only a very small leakage air flow 36 would flow via the shingle edge 31 from the intermediate space 35 should the shingle edge 31 be sealed very insufficiently against the combustion chamber wall 32.

FIGS. 7 and 8 respectively show a simplified top view of the embodiment according to the invention in a schematic rendering. Here, in particular the shingle edge 31 is shown, which provides a seating surface of the shingle, as shown in FIGS. 4 to 6. A field of impingement cooling holes is indicated by the reference sign 37, without describing the individual impingement cooling holes and their arrangement. They can be arranged in a suitable manner, with the particular arrangement of impingement cooling holes not playing a decisive role for the invention. Rather, what is important here is that a distance A, in which no impingement cooling holes and thus no impingement perforation is present, results between the side of the shingle edge 31 that is facing towards the arrangement of impingement cooling holes 34. FIGS. 7 and 8 show the inner side of the shingle edge 31 as edge R1 or R2. Further, FIGS. 7 and 8 respectively show the distance A between the edge R1 or R2 and a boundary G of the field 37 of the impingement cooling holes.

As shown in FIG. 7, the distances A add up at the edges of the field 37 according to the invention, resulting in a beveling of the field 37. Thus, the edge distances A add up in such a manner in the edges of the shingle 25, that a value A results if a distance from the first edge R1 of the seating surface of the shingle edge 31 of the shingle 25. A value A also results from the second edge R2 of the seating surface of the shingle edge 31 of the shingle. Thus, the field 37 of the impingement cooling holes (impingement cooling pattern) ends along a line L1 that is parallel to the edge R1, and at a distance along a line L2 that is parallel to the edge R2. In this manner, the distance A is defined. The boundary of the field 37 of the impingement cooling holes is indicated by G as a dashed line. In the corners, the field 37 of the impingement cooling pattern has a distance of C×A on the line L1 along the edge R1. Analogously, a distance of C×A results regarding the edge R2 and the line of the boundary G of the impingement cooling pattern. The factor C is defined as an overlay constant, and generally lies between 1.1 and 3, preferably between 1.5 and 2.5, ideally 2. With C=1 (state of the art), the impingement perforation along the line L1 would reach to the edge R2 up to the intersection with line L2. FIG. 7 shows an ideal state with a distance of 2×A from the impingement cooling perforation along the line L1 to the edge R2. As shown in FIG. 7, the result is additional corner area in the shape of an equilateral triangle, with no impingement cooling holes being provided therein.

FIG. 8 shows a variant in which the field 37 of the impingement cooling holes is rounded off in the corner area, so that the boundary G extends in the form of a circular arc in this location.

According to the invention, the openings for the impingement cooling are thus placed at a distance A from the edge of the shingle in order to avoid any edge leakages from an impingement-effusion-cooled shingle, so that effusion cooling holes can be arranged between the impingement cooling opening that is closest to the edge and the inner side of the edge of the shingle so as to ensure an outflow of cooling air from the impingement cooling holes through the effusion cooling holes, and to avoid any edge leakage. The distance from the edge of the shingle, in which no impingement cooling holes are provided, is at least 2 times the free path length of the impingement cooling jet within the intermediate space formed by the shingle. 

1. A chamber of a gas turbine, with at least one shingle that comprises a plate-shaped shingle body having a circumferential shingle edge which is raised from the side that is facing away from the combustion chamber interior space, and which abuts against a combustion chamber wall in the mounted state of the shingle, wherein the shingle body is provided with an arrangement of effusion cooling holes, and the combustion chamber wall is provided with an arrangement of impingement cooling holes in the area of the shingle, wherein the arrangement of impingement cooling holes has a lateral distance to the shingle edge which is between 1.5 and 2 times the distance of the surface of the combustion chamber wall to the surface of the shingle body, and in that the distance of the arrangement of impingement cooling holes is between 1.1 and 3 of the lateral distance in the corner areas of the shingle.
 2. The combustion chamber according to claim 1, wherein the distance in the corner areas is between 1.5 and 2.5 of the distance.
 3. The combustion chamber according to claim 1, wherein the corner area of the arrangement of impingement cooling holes is embodied in a linear manner.
 4. The combustion chamber according to claim 1, wherein the corner area of the arrangement of impingement cooling holes is embodied in a rounded-off manner.
 5. The combustion chamber according to claim 1, wherein the arrangement of effusion cooling holes comprises the entire shingle body.
 6. The combustion chamber according to claim 5, wherein effusion cooling holes are arranged inside the distance (A).
 7. The combustion chamber according to claim 5, wherein the ratio of the number of impingement cooling holes to the number of effusion cooling holes is 1:1 to 1:3.
 8. The combustion chamber according to claim 7, wherein respectively at least one row of effusion cooling holes is arranged inside the distance, wherein the number of rows of effusion cooling holes inside the distance corresponds to the ratio of the number of impingement cooling holes to the number of effusion cooling holes. 